Multiple things:

1. We removed all the function/methods/tests that were used to
create and manage rook legacy OSDS as well as bringing support to
Bluestore OSD only.
It also fixes various go-lint issues in the respectives files.

2. use c-v inventory to detect available devices:
Now we rely on the 'ceph-volume inventory' command to tell us if a
device is available or not.

3. implement raw mode for osd on pvc
When an OSD will be bootstrap on a PVC, the new c-v raw mode will be
used. It consists of putting block, db and wal under the same device.
Here LVM is out of the picture and the raw device is used as is. The
implementation is backward compatible so existing OSD on PVC will LVM
will continue to operate.

Closes: https://github.com/rook/rook/issues/4363

Signed-off-by: Sébastien Han <seb@redhat.com>